The overall objective of this grant is to determine the biochemical basis of the pathogenesis of the secondary sequelae of diabetes mellitus. We have been studying as a model reaction the glycosylation of hemoglobin. In order to understand this mechanism better we have unambiguously assigned the structure of hemoglobin AIc (Hb AIc) and found it to have the same structure as hemoglobin A except for the addition of I deoxy, 1-(N-valyl) fructose attached to the amino terminus of the beta-chain. Additional insight was gained in the past year by studying the mechanism of formation of glycosylated hemoglobins. It has been possible to form glycohemoglobins nonenzymatically by having phosphorylated glycolytic intermediates react with hemoglobin to form covalent adducts. The two requirements for adduct formation are a phosphate and a free aldehyde or ketone. Additional effort has been spent in the past year in understanding the biochemical basis of the defect associated with the platelets in the diabetic state. It has been found that the length of the secondary lag phase of platelet aggregation following stimulation with epinephrine increased from a mean of 19 seconds to 65 seconds following institution of strict carbohydrate control in diabetic patients. This reversible hematological finding using hemoglobin AIc as a monitor of carbohydrate control of diabetes points to the utility of this measurement in monitoring the degree of control of diabetes mellitus. Hopefully, in the future it will be possible to correlate other clinical sequelae of diabetes with Hb AIc concentration. BIBLIOGRAPHIC REFERENCES: Koening, R.J., Blobstein, S.H. and Cerami, A.: Structure of the carbohydrate of hemoglobin AIc. J. Biol. Chem. 252:2992-2997, 1977. Stevens, V.S., Vlassara, H., Abati, A. and Cerami, A.: Nonenzymatic glycosylation of hemoglobin. J. Biol. Chem. 252:2998-3002, 1977.